Sure there are. For example, your bundle size shrinks when targeting newer browsers because more features exist, fewer need to be polyfilled.
Then you must prepare two bundles, one for new browsers and one for old. I suppose that's possible, but doesn't seem worth it.
You can use <script type=module> to target newer browsers. It’s definitely worth having two bundles because the ES6 and newer is much smaller. And one day, you stop shipping the old ES5 bundle.